V = IR

See if you can recall the units and symbol for the following terms:

Current, voltage, energy, power, resistance, time

Power = current x voltage

P=IV

Draw a series of diagrams to show how the movement of the electrons in a wire carrying an electric current makes that wire get hot, by explaining what happens to the atoms.

Energy = current x voltage x time

Wire

Bulb

Start with the atoms in a lattice like this one …

OOOOOO

OOOOOO

… and then bring in a current of electrons o o o o o o o like this!

E=IVt

Sage and scribe

Complete the worksheet in pairs

Post it note challenge

3 different difficulties. Answer at least two from each. Take completed ones from the board and check them.

Can you think of 5 devices where the heating effect of electric current is useful?

What is resistance?

I want my air conditioning to come on when it gets hot.

Resistance makes the wire or the resistor get hot. Why might this be?

What disadvantages does it have?

As things get hotter the resistance increases. What do you think causes this?

Rheostat

Plot the following graphs

V = IR

Diode

Voltage vs current

for a filament bulb

Voltage vs current for a diode

Voltage vs current for a resistor

How does the volume control on a radio work?

Sketch each of these and explain how current voltage and resistance change.

Voltage = current x resistance

Complete the tarsia

Investigation

Plot the graph

How does the length of a wire affect its resistance?

Measure the resistance for various lengths of wire and then plot length vs resistance